1. Field of Invention
The present invention relates to a shooting parameter adjustment method, and more particularly to a shooting parameter adjustment method for face detection.
2. Related Art
Nowadays, an image capturing device has been widely used in the daily life. The image capturing device captures images by using a photo-sensor and converts the images into digital signals, and the digital signals can be stored. Various applications are designed with the digital signals captured by the image capturing device in combination with digital image processing techniques.
The human image is the core of images captured by the image capturing device. For example, currently, many image capturing devices have face detection and face tracking techniques, which assist in automatic multi-focusing of a shot region. In addition, the face detection technique may also be used for determining human presence in a specific region. For example, the face detection technique can be applied to determine whether a user is watching a television (TV) screen in front of the TV screen. When it is determined by the face detection technique that currently nobody is in front of the TV screen, the TV screen can be automatically turned off to achieve the efficacy of energy saving.
However, when an image capturing device shoots an image, a method for calculating a shooting parameter (a shutter value or an aperture value) is usually single-point photometry or average photometry. Since the position of a face cannot be known in advance before face detection is performed, the face may appear too bright or too dark in the above photometry. For example, when shot against the light source, the brightness of the face is far lower than that of the background. On the contrary, when shot facing the light source, the brightness of the face is much higher than that of the background. In the case that the brightness of the face is excessively high or low, relevant features in the image of the face may be lost due to overexposure or underexposure of the features of the face.